JAM pedals are used by Bernie Marsden, Dweezil Zappa and Nels Cline among others.
Each has circuitry based on classic '60s and '70s vintage pedals using high-quality (often NOS) components. This Wahcko Plus, for example, features a red Fasel inductor, carbon-comp resistors, tropical fish capacitors and a highly-specified pot.
This is an expressive and vocal wah with a lovely smooth sweep through any of the six selectable frequency ranges on its six-position rotary switch. It also provides a useful range of treble boosts.